How to determine which preference file lock a Firefox config option

On a Windows 7 computer, My Firefox network.proxy.type is locked so I cannot modify it When looking at C:\Program Files (x86)\Mozilla Firefox\default/prefs/localsettings.js there are only 2 lines:

pref("general.config.obscure_value", 0);

pref("general.config.filename", "config.cfg");

Then when looking at config.cfg there is no line looking like

lockPref("network.proxy.type", 5);

and when I try to add my own preference with an other value

pref("network.proxy.type", 2); I see in firefox that the preference is locked and don't take my value in account.

I also looked inside about:support to determine my profile directory and looked in every .cfg and .js files but still no lockPref that could explain why network.proxy.type is locked

Is there a way to know from which configuration file the lock is coming ? During my web search I found a lot of pages explaining how to lock some options etc but nothing on how to understand why an option is locked

Thanks by advance for your help

2 Answers

If you're in an enterprise Windows environment, it's possible that the setting has been enforced using a Group Policy Object rather than through config files.

If so, you should be able to dig up the the relevant setting from somewhere around HKLM\Software\Policies\Mozilla\Firefox\Proxy in the Windows Registry.

If you want an approach to modifying the value that's GPO resistant, note that it's possible (in 60.6.1esr) to trick Firefox into not making use of the registry values by modifying the binary Mozilla Firefox/browser/omni.ja accordingly (just search for network.proxy.type). Note also that modifying it too much (e.g. changing its length) will just cause Firefox to crash when opened.

1. Close Firefox
2. Navigate to C:\Program Files (x86)\Mozilla Firefox
3. Modify the mozilla.cfg file.
4. Remove any LockPref you no longer want.
5. Save As to Desktop.
6. Replace old mozilla.cfg with your new mozilla.cfg file
7. Restart Firefox